/*
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2011 Red Hat, Inc. All rights reserved.
 * Written by Karel Zak <kzak@redhat.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * mountpoint(1) - see if a directory is a mountpoint
 *
 * This is libmount based reimplementation of the mountpoint(1)
 * from sysvinit project.
 */
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <getopt.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <libmount.h>

#include "nls.h"
#include "xalloc.h"
#include "c.h"
#include "closestream.h"
#include "pathnames.h"
#include "mount-api-utils.h"

#define MOUNTPOINT_EXIT_NOMNT	32

struct mountpoint_control {
	char *path;
	char *mnt_target;
	dev_t dev;
	struct stat st;
	struct libmnt_cache *cache;
	bool	dev_devno,
		fs_devno,
		nofollow,
		quiet,
		show;
};

#ifdef HAVE_STATMOUNT_API
/*
 * dir_to_device_statmount - check if path is a mountpoint using statmount()
 * @ctl: mountpoint control structure
 *
 * Returns: <0 on error, 0 if mountpoint, 1 if not a mountpoint
 */
static int dir_to_device_statmount(struct mountpoint_control *ctl)
{
	struct libmnt_fs *fs = NULL;
	const char *mnt_target;
	char *cn = NULL;
	uint64_t id = 0;
	int rc;

	cn = mnt_resolve_path(ctl->path, ctl->cache);

	rc = mnt_id_from_path(cn ? cn : ctl->path, &id, NULL);
	if (rc)
		goto done;

	fs = mnt_new_fs();
	if (!fs) {
		rc = -ENOMEM;
		goto done;
	}

	mnt_fs_set_uniq_id(fs, id);

	rc = mnt_fs_fetch_statmount(fs, STATMOUNT_MNT_POINT | STATMOUNT_SB_BASIC);
	if (rc)
		goto done;

	mnt_target = mnt_fs_get_target(fs);
	if (!mnt_target) {
		rc = -EINVAL;
		goto done;
	}

	if (ctl->show)
		ctl->mnt_target = xstrdup(mnt_target);

	if (strcmp(mnt_target, cn ? cn : ctl->path) != 0)
		rc = 1;	/* not a mountpoint */
	else {
		ctl->dev = mnt_fs_get_devno(fs);
		rc = 0;	/* is a mountpoint */
	}
done:
	mnt_unref_fs(fs);
	return rc;
}
#endif /* STATMOUNT_MNT_POINT */

/*
 * dir_to_device - check if path is a mountpoint
 * @ctl: mountpoint control structure
 *
 * Returns: <0 on error, 0 if mountpoint, 1 if not a mountpoint
 */
static int dir_to_device(struct mountpoint_control *ctl)
{
	struct libmnt_table *tb;
	struct libmnt_fs *fs;
	int rc;

#ifdef HAVE_STATMOUNT_API
	rc = dir_to_device_statmount(ctl);
	if (rc >= 0)
		return rc;
#endif
	/*
	 * Fallback for older kernels without statmount() support
	 */
	if (ctl->show)
		errx(EXIT_FAILURE, _("--show is not supported on this system"));

	tb = mnt_new_table_from_file(_PATH_PROC_MOUNTINFO);
	if (!tb) {
		/*
		 * Fallback. Traditional way to detect mountpoints. This way
		 * is independent on /proc, but not able to detect bind mounts.
		 */
		struct stat pst;
		char buf[PATH_MAX];
		const char *cn;
		int len;

		cn = mnt_resolve_path(ctl->path, ctl->cache);	/* canonicalize */

		len = snprintf(buf, sizeof(buf), "%s/..", cn ? cn : ctl->path);

		if (len < 0 || (size_t) len >= sizeof(buf))
			return -EINVAL;

		rc = stat(buf, &pst);
		if (rc)
			return -errno;

		if (ctl->st.st_dev != pst.st_dev || ctl->st.st_ino == pst.st_ino) {
			ctl->dev = ctl->st.st_dev;
			return 0;	/* is a mountpoint */
		}

		return 1;	/* not a mountpoint */
	}

	/* to canonicalize all necessary paths */
	mnt_table_set_cache(tb, ctl->cache);

	fs = mnt_table_find_target(tb, ctl->path, MNT_ITER_BACKWARD);
	if (fs && mnt_fs_get_target(fs)) {
		ctl->dev = mnt_fs_get_devno(fs);
		rc = 0;	/* is a mountpoint */
	} else
		rc = 1;	/* not a mountpoint */

	mnt_unref_table(tb);
	return rc;
}

static int print_devno(const struct mountpoint_control *ctl)
{
	if (!S_ISBLK(ctl->st.st_mode)) {
		if (!ctl->quiet)
			warnx(_("%s: not a block device"), ctl->path);
		return -1;
	}
	printf("%u:%u\n", major(ctl->st.st_rdev), minor(ctl->st.st_rdev));
	return 0;
}

static void __attribute__((__noreturn__)) usage(void)
{
	FILE *out = stdout;
	fputs(USAGE_HEADER, out);
	fprintf(out,
	      _(" %1$s [-qd] /path/to/directory\n"
		" %1$s -x /dev/device\n"), program_invocation_short_name);

	fputs(USAGE_SEPARATOR, out);
	fputs(_("Check whether a directory or file is a mountpoint.\n"), out);

	fputs(USAGE_OPTIONS, out);
	fputs(_(" -q, --quiet        quiet mode - don't print anything\n"
		"     --nofollow     do not follow symlink\n"
		" -d, --fs-devno     print maj:min device number of the filesystem\n"
		" -x, --devno        print maj:min device number of the block device\n"
		"     --show         print mountpoint for given path\n"), out);
	fputs(USAGE_SEPARATOR, out);
	fprintf(out, USAGE_HELP_OPTIONS(20));
	fprintf(out, USAGE_MAN_TAIL("mountpoint(1)"));

	exit(EXIT_SUCCESS);
}

int main(int argc, char **argv)
{
	int c, rc;
	struct mountpoint_control ctl = { NULL };

	enum {
		OPT_NOFOLLOW = CHAR_MAX + 1,
		OPT_SHOW
	};

	static const struct option longopts[] = {
		{ "quiet",    no_argument, NULL, 'q' },
		{ "nofollow", no_argument, NULL, OPT_NOFOLLOW },
		{ "fs-devno", no_argument, NULL, 'd' },
		{ "devno",    no_argument, NULL, 'x' },
		{ "show",     no_argument, NULL, OPT_SHOW },
		{ "help",     no_argument, NULL, 'h' },
		{ "version",  no_argument, NULL, 'V' },
		{ NULL, 0, NULL, 0 }
	};

	setlocale(LC_ALL, "");
	bindtextdomain(PACKAGE, LOCALEDIR);
	textdomain(PACKAGE);
	close_stdout_atexit();

	mnt_init_debug(0);

	while ((c = getopt_long(argc, argv, "qdxhV", longopts, NULL)) != -1) {

		switch(c) {
		case 'q':
			ctl.quiet = 1;
			break;
		case OPT_NOFOLLOW:
			ctl.nofollow = 1;
			break;
		case 'd':
			ctl.fs_devno = 1;
			break;
		case 'x':
			ctl.dev_devno = 1;
			break;
		case OPT_SHOW:
			ctl.show = 1;
			break;

		case 'h':
			usage();
		case 'V':
			print_version(EXIT_SUCCESS);
		default:
			errtryhelp(EXIT_FAILURE);
		}
	}

	if (optind + 1 != argc) {
		warnx(_("bad usage"));
		errtryhelp(EXIT_FAILURE);
	}
	if (ctl.nofollow && ctl.dev_devno)
		errx(EXIT_FAILURE, _("%s and %s are mutually exclusive"),
		     "--devno", "--nofollow");

	ctl.path = argv[optind];
	c = ctl.nofollow ? lstat(ctl.path, &ctl.st) : stat(ctl.path, &ctl.st);
	if (c) {
		if (!ctl.quiet)
			err(EXIT_FAILURE, "%s", ctl.path);
		return EXIT_FAILURE;
	}
	if (ctl.dev_devno)
		return print_devno(&ctl) ? MOUNTPOINT_EXIT_NOMNT : EXIT_SUCCESS;

	if (ctl.nofollow && S_ISLNK(ctl.st.st_mode)) {
		if (!ctl.quiet)
			printf(_("%s is not a mountpoint\n"), ctl.path);
		return MOUNTPOINT_EXIT_NOMNT;
	}

	ctl.cache = mnt_new_cache();
	if (!ctl.cache)
		err(EXIT_FAILURE, _("failed to initialize libmount cache"));

	rc = dir_to_device(&ctl);
	if (rc < 0) {
		if (!ctl.quiet) {
			errno = -rc;
			warn("%s", ctl.path);
		}
		rc = EXIT_FAILURE;
		goto done;
	}

	if (ctl.show) {
		printf("%s\n", ctl.mnt_target);
		rc = EXIT_SUCCESS;
		goto done;
	}

	if (rc == 1) {
		if (!ctl.quiet)
			printf(_("%s is not a mountpoint\n"), ctl.path);
		rc = MOUNTPOINT_EXIT_NOMNT;
		goto done;
	}

	if (ctl.fs_devno)
		printf("%u:%u\n", major(ctl.dev), minor(ctl.dev));
	else if (!ctl.quiet)
		printf(_("%s is a mountpoint\n"), ctl.path);

	rc = EXIT_SUCCESS;

done:
	free(ctl.mnt_target);
	mnt_unref_cache(ctl.cache);
	return rc;
}
